Agricultural application of arsenate-based pesticides from the 1890s through 1970s left significant acreage of arsenic residues particularly on land used for apple, potato, and blueberry farming. Arsenate was applied at rates up to 80 kg ha-1 in most fruit orchards until insecticides such as DDT were introduced the late 1940s resulting in contamination over large areas. These wide-area and smaller localized areas of arsenic contaminated soils are difficult and expensive to remediate via conventional means. An alternative approach is phytoremediation, using living plants to extract and concentrate the element from contaminated soils and waters. The arsenic accumulating Edenfern(tm) plants have been used commercially to decrease arsenic concentrations at a number of sites. Because the ferns are native to semi-tropical environments their use in northern or temperate climates is restricted to annual plantings that increase cost. Endophytic bacteria and fungi that colonize specific plants have been shown to confer tolerance to adverse conditions, improve plant nutrient utilization, increase disease resistance, and facilitate degradation of soil and water contaminants such as TCE and PAHs. An understanding of the many benefits conferred by endophytic organisms is still developing and recently the Doty laboratory isolated endophytes from plants growing on arsenic contaminated soils within the Tacoma Smelter Plume in Washington State. These bacterial endophytes have shown an unusual tolerance to arsenic and may provide improved arsenic accumulation in phytoremediation applications. This project seeks to address wide area arsenic contamination through the use of conventional (non-transgenic) endophytes that improve arsenic tolerance and uptake in woody biomass crops such as willow for phytoremediation. The use of novel endophytes isolated from native plants found on arsenic contaminated soils generates a technology approach that will allow a variety of crops and cropping systems to be used for phytoremediation. The Phase I approach provides a strong basis for Phase II work which if successful will provide site managers with an invaluable, low-cost tool for removal of arsenic from contaminated soils.
This Phase I project seeks to reduce the cost of remediating soils contaminated with arsenic by developing a plant:endophyte system using willow plants with an improved ability to tolerate and accumulate arsenic from the soil. The project focuses on using naturally occurring bacterial endophytes found in plants growing on arsenic contaminated sites to increase tolerance to arsenic in a crop plant suited for phytoremediation to allow cost effective treatment of wide area contamination.
